Pure dolomite rock is entirely composed of the mineral dolomite, which is a solid solution of calcium and magnesium carbonate with the formula CaMg(CO.sub.3).sub.2. Dolomite sinter, produced from dolomite by means well-known in the art, consists of approximately 40 weight percent MgO and 60 weight percent CaO and possesses a continuous CaO matrix with isolated pockets of MgO.
Because the calcium oxide tends to hydrate faster than magnesia and also because calcium oxide has a lower resistance to high iron slags, it is desirable to increase the MgO concentration in dolomite sinter to produce a refractory having a continuous MgO matrix. Dolomite sinter of increased MgO content is referred to in the art as synthetic magnesite-dolomite sinter. Such synthetic sinter, having a higher hydration and slag resistance than ordinary dolomite, represents an excellent refractory material for basic oxygen furnace linings, especially when high iron slags are involved.
The prior art describes various processes for the production of magnesite-dolomite sinter from dolomite. One such process adds a magnesium hydroxide (Mg(OH).sub.2), commonly called brucite, slurry to hydrated dolomite to increase the magnesia (MgO) content. In another process, calcium compounds are chemically dissolved from the dolomite to produce a synthetic sinter containing up to 98% pure MgO.
The present process invention distinguishes over all known prior art processes directed to the production of synthetic magnesite-dolomite sinter by utilizing the different hydration rates of calcium hydroxide (Ca(OH).sub.2), commonly called portlandite, and Mg(OH).sub.2. Further, the method of the present invention is relatively inexpensive and lends itself to large scale production. The inventive process increases magnesia content in dolomite sinter up to about 75% by weight.